21 March 2007

The tech, as per protocol, dropped the ECG on my desk within three minutes of its being completed, along with the chart. He was visibly excited. I glanced at the ECG and the triage note. In the standard terse nursing verbiage, it read "CC: Ground Level Fall. Too weak to get out of bed. No injury reported. No other complaints." There was an included prior ECG, which was normal. Today's looked like this:"Should I call the cath lab?" the tech asked. We pride ourselves in having the best door-to-dilation time in the region, and it's a key focus of our department protocols that patients with an "Acute MI" or heart attack need to be expedited to the cath lab. The tech had seen the computer interpretation of "ACUTE MI" and was rarin' to go.

I have learned not to trust the computer. The only thing it can reliably interpret is "Normal" and even then it is sometimes wrong.

So, as several of the commenters correctly guessed, I ordered a stat chemistry panel, and the serum potassium was resulted at 8.5 (normal = 3.5-4.5), which should not be surprising because, once I took the drastic step of meeting and interviewing the patient, he has kidney failure and is dialysis dependent. He was too weak to get out of bed for dialysis and so had missed his appointment, which was part of the reason his potassium was elevated. The other part? I'll get to that.

So, hyperkalemia (medicalese for "high potassium") is one of those things that is a true emergency, that can be immediately lethal if not treated, and one of the few things that really gets an ER doctor moving. Potassium is involved in maintaining the electrical gradient which allows muscle and nerve cells to function -- excessive potassium in the bloodstream poisons the ability of these cells to operate normally. This accounts for the patient's generalized weakness. The Bad Thing that can happen is that the heart muscle can be affected -- in this case, the heart muscle was no longer contracting briskly in unison over the usual 100 milliseconds or so, but rather contracting sluggishly over a period of 200 msec; you can see how wide and ugly the spikes (QRS complex) are on the above ECG. It was still pumping OK, but the risk is that this makes the heart very vulnerable to arrhythmia, that any minor disruption, like a premature beat, could induce irrecoverable ventricular fibrillation.

Fortunately for adrenaline junkies like me, there is an antidote: a cocktail of Calcium, Sodium Bicarbonate, and insulin, which can very quickly mitigate the effects of hyperkalemia. the bicarb and insulin activate ion pumps which move the potassium inside of cells, which temporarily "hides" the excess potassium from the heart. Calcium buffers the heart cell membranes and stabilizes them from the ill effects of the potassium. It's extremely gratifying. It doesn't fix the problem, but generally buys you enough time to get the patient to dialysis, which will remove the potassium from the bloodstream. Calcium works fastest and should always be given first in these situations. Here's how it worked for us:And the after-treatment ECG:Notice the nice narrow QRS complexes. Much better looking. And off he went for emergency dialysis.

And as for the "why" -- well, he had a dedicated and caring wife. She was very concerned about the general decline in his health since he had been on dialysis, and that in particular he was losing weight and malnourished because he no longer had the appetite he once did. So over the weekend, she went and got him some really nutritious vegetable juice -- V8.Chock full o' potassium. 470 mg per serving. Sheesh.

Shadowfax

About me: I am an ER physician and administrator living in the Pacific Northwest. I live with my wife and four kids. Various other interests include Shorin-ryu karate, general aviation, Irish music, Apple computers, and progressive politics. My kids do their best to ensure that I have little time to pursue these hobbies.

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